GARDEN ESCAPE ARTISTS Many Frequently-Planted Garden Plants Cause Trouble in the Wild

BLUE RIDGE PARTNERSHIP FOR REGIONAL INVASIVE SPECIES MANAGEMENT www.blueridgeprism.org April 2018

Your Garden Matters Which plants you grow around your home matters in ways most people cannot begin to imagine. Many of the worst nonnative, invasive plants plaguing our natural and agricultural areas began their careers in home gardens or landscape settings. Some were – and most still are – sold and promoted for their showy beauty, fast growth, or bird- or butterfly-attracting attributes. Easy to grow and satisfying to look at, these innocent-seeming plants aren’t content to remain where they are planted. They escape from their garden settings, multiply, and cavort in places where they were never meant to be. And in the process, once they are “introduced” into the native landscape, they displace native plants that are the basis for the food chains that sustain the natural kingdom. Nonnative ornamental pear trees now occur as weed trees up and down Perilla mint, also called the roadsides in the Mid-Atlantic States, having escaped from nearby beefsteak plant, (Perilla fru- suburban yards and shopping malls. tescens) is a good example of an introduced garden plant Birds such as starlings (also an introduced species) devour the gone badly wild. Valued fruits; the seeds in the fruits pass right through the birds. The tree both as a medicinal herb, thus escapes neighborhoods where it is used as a lawn or street salad green, and showy foli- tree and gets planted all over the built and natural landscape. It is age plant, this mint family especially prolific in disturbed areas. Today, this invasive tree lines annual probably escaped highways, fills vacant lots, and encroaches on fields and pastures from gardens many times up and down the East Coast. and in many places. Now it Perilla mint and ornamental pear are only two examples of the many garden plants that are bad actors in natural sites. Of course, The purple-leaf variety of perilla mint grows aggressively where it not all garden and landscape plants are invasive. Most stay put. is favored by gardeners as a dependa- is not wanted as an invader The concern comes from those plants that can readily escape culti- ble splash of colorful foliage. If you of floodplain, alluvial, and vation and run rampant. must plant it, always remove all flow- mesic forests, where it can er spikes before they set seed. form dense monotypic stands. It also invades hay- Invasives for Sale fields and pastures; it is toxic Unfortunately, many of the worst invasives, including about half to livestock if they eat it fresh, of the PRISM’s Terrible Twelve Invasives, are commonly sold in less so in hay. Ingested by garden centers and nurseries in Virginia and other states. Virgin- cattle, the herb causes severe ia’s Department of Conservation and Recreation (DCR) lists 90 respiratory distress called nonnative plant species that are invasive in the commonwealth. panting disease. This medicinal Approximately two-thirds of these are frequently planted in gar- plant has spread aggressively dens or landscapes, and only a few of them are banned from sale throughout the eastern U.S., in Virginia. Many other states have much tougher regulations especially in the Mid-Atlantic governing the sale and importation of invasive plants than does and South. Naturalized Virginia. And they enforce them with hefty fines. Purple- and green-leaf forms of perilla stands of perilla crowd out mint grow here next to a forest path. native plants that are a source Beware the New of food for wildlife. This de- Avid gardeners often seek the newest and latest plants and plant struction all began innocently by people planting something pretty trends. Some go for anything new and unusual to enjoy and dis- or edible in their gardens. play in their gardens. Unfortunately, some new garden plants may The ornamental pear, often called Callery or Bradford pear, is pose an unseen danger to our native landscapes. And, as with the another disaster story that began innocently. The Bradford pear, a Bradford pear, it may be years before their threat becomes evident; cultivar of Pyrus calleryana, was first sold and promoted to the by then it may be too late. public in the 1960’s by the USDA. Its prolific white spring flowers, Incised fumitory (Corydalis incisa) is an example of a “new” flaming fall foliage, and neat oval shape seemed to offer a tree well garden plant that is now threatening natural areas in several states. suited to home and public spaces. But the ornamental tree had This showy, spring-bloomer from Asia, which draws admirers several drawbacks that were not observed until it was widely with its spires of lavender-pink flowers, was sold in the U.S. only planted. Thought to be sterile, the ornamental pear tree actually by one specialty mail-order nursery about 15 years ago. The plant produces great quantities of pea-sized green “pears” when cross- was first noted in the wild in 2005 by citizen scientists conducting pollinated. a survey along the Bronx River in New York. No one knows from

whose garden the pretty plant Nandina domestica (heavenly bamboo) first escaped. Reynoutria japonica syn. Fallopia japonica (Japanese knotweed) Recently, incised fumewort Spirea japonica & S. x bumalda (spirea, meadowsweet) was found growing in several Viburnum dilatatum (linden viburnum) & V. setigerum (tea viburnum) natural sites from New York to Virginia, where it was creating VINES & GROUNDCOVERS dense stands that crowded out Actinidia argutus (hardy kiwi) the wildflowers. Incised fume- Ajuga reptans (bugleweed) Akebia quinata (five-leaf akebia) Incised fumewort fumewort spreads by explosive seedpods. When ripe, the pods Ampelopsis brevipedunculata (porcelainberry) burst and shoot hundreds of tiny, black seeds as far away as nine Celastrus orbiculatus (Oriental bittersweet) feet. Wildlife biologists fear this invasive will form extensive popu- Clematis ternata syn. C. maximowiziana (sweet autumn clematis) lations that could carpet the forest floor throughout the East, oblit- Euonymus fortunei & cultivars (wintercreeper) erating all wildflowers in its path. Early-detection-and-rapid- Hedera helix (English ivy) response actions could stop the plant’s spread if authorities act Houttunyia cordata (chameleon plant) soon enough and are adequately funded. Ipomea coccinea (cardinal climber) Ipomea purpurea and other species (morning glory) Lonicera japonica (Japanese honeysuckle) Know What You Grow Vinca minor (periwinkle, myrtle) Most garden plants stay where they are planted and don’t pose a Vincetoxicum rossicum (swallowwort) danger to natural areas. However, just because a nonnative plant is Wisteria chinensis & W. japonica (Chinese & Japanese wisteria) not invasive is not reason enough to grow it. If you were to substi-

tute a native tree for a nonnative one, you would be doing a good TREES deed for Mother Nature. For instance, Japanese zelkova, a popular Acer platinoides & cultivars (Norway maple) street tree, supports no insects and thus does not provide any bird Albizia julibrissin (mimosa, silktree) food – almost all bird species feed their hatchlings insects. A na- Koelreuteria paniculata (golden rain tree) tive oak tree supports close to 500 different caterpillar species! And Paulownia tomentosa (princess tree) those caterpillars, which are preyed upon by birds and other in- Phellodendron amurense (Amur corktree) sects, hatch into moths and butterflies that pollinate other plants. Pyrus calleryana & cultivars (Bradford pear, ornamental pear) It is possible to both have your plants and to garden responsi- Quercus acutissima (sawtooth oak) bly. Growing locally native plants in your home garden and land- Sophora japonica (Japanese pagoda tree) scape is the very best way to have it all – beautiful grounds around Styrax japonicus (Japanese snowbell) your home and thriving natural areas where Nature can flourish. Ulmus parvifolia (lacebark elm) & U. siberica (Siberian elm) Some nonnative invasive plants pose a danger only if they are planted next to or near a natural area. If you live in a city and are ORNAMENTAL GRASSES not near a park, what you grow may not be important because Arundo donax (giant reed) there is nowhere for potentially invasive plants to escape. And if Bambusa & Phyllostachys species & cultivars (bamboo) you live near a vulnerable area, some plants with the potential to Imperata cylindrica & cultivars (cogongrass, Japanese bloodgrass) escape may be okay as long as you never let them set seed – ever! Miscanthus sinensis & cultivars (Chinese silver grass, miscanthus) Most garden escape artists offer clues to their intentions. Be Pennisetum alopecuroides & cultivars (fountain grass) wary of any nonnative garden plant that is: Pennisetum setaceum & cultivars (crimson fountain grass)  Weedy within your garden – it can escape to natural areas  Supposed to attract birds with showy berries – birds will GARDEN PERENNIALS & ANNUALS spread it outside your property Aegopodium podagraria (goutweed)  Advertised as easy to “naturalize” – that word really Arum italicum (Italian arum) means it can be weedy and escape Campanula rapunculoides (creeping bellflower)  Included in a “meadow garden” mix – such plants may Centaura cyanus (annual cornflower) be prolific seeders and will escape Corydalis lutea (yellow fumewort)  Contained in a “wildflower” mix – these plants are rare- Ficaria verna (lesser celandine) ly native wildflowers and can harm the environment Glechoma hederacea (ground ivy)  Touted as good for erosion control – translate this to Hesperis matronalis (dame’s rocket) mean it spreads aggressively by its roots Hyacinthoides hispanica (Spanish bluebells) Iris pseudoacorus (yellow water iris) Please Do Not Grow These Plants Lamiastrum galeobdolom (yellow archangel) The following garden plants are known to become invasive. Lamium maculata (spotted deadnettle) Lathyrus latifiolius (everlasting pea) SHRUBS Lunaria annua (honesty) Berberis thunbergii & cultivars (Japanese barberry, purple barberry) Lythrum salicaria & L. virgatum & cultivars (purple loosestrife) Buddleia davidii (butterfly bush) Cytisus scoparius (Scotch broom) EDIBLE & MEDICINAL HERBS Eleagnus angustifolia (Russian olive) Alliaria petiolata (garlic mustard) Eleagnus umbellata (autumn olive) Foeniculum vulgare (fennel) Euonymus alatus (burning bush, winged euonymus) Hypericum perforatum (common St. John’s wort) Hibiscus syriacus (rose-of-Sharon) Melissa officinalis (lemon balm) Ligustrum sp. (privet) Perilla frutescens (perilla mint, beefsteak plant) Lonicera tatarica & L. morrowii (bush honeysuckle) Valeriana officinalis (common valerian) Text and photos by Susan Austin Roth © 2018 Shenandoah National Park Trust